The occurrence of epidermoids within the spinal canal is uncommon. Most of the reported spinal epidermoids (SEs) have been described in the thoracic or lumbar regions. They occur either following trauma or in the setting of coexistent spinal dysraphism. The authors describe an unusual case of a 28-year-old lady who presented with long-standing back pain and urinary incontinence. Magnetic resonance imaging (MRI) of her spine demonstrated a sacral SE without any coexistent spinal dysraphism. The diagnosis of an epidermoid was confirmed by histopathological examination following laminectomy and excision. To the authors' best knowledge, this is the third case of a sacral SE occurring in a non-dysraphic spine. The case is discussed in the light of a relevant literature review.

Spinal epidermoids (SEs) are uncommon tumors, constituting less than 1% of all intraspinal tumors. [1] Their occurrence in the sacral region is unusual. [1],[2],[3],[4],[5],[6],[7],[8],[9] Most of the sacral SEs have been reported either in conjunction with anterior sacral meningoceles, as a component of Currarino syndrome (CS), [10],[11],[12],[13],[14] or as sequelae to lumbar punctures. [9],[15] This report of a patient with a primary, nonsyndromal sacral SE in the absence of coexistent spinal dysraphism or preceding trauma is the third of its kind in indexed literature.

Case report

Clinical presentation and examination

A 28-year-old lady presented with low backache since childhood and urinary incontinence of a duration of 1 year. There was no history of weakness or numbness in the limbs, meningitis, lumbar puncture, or trauma to the spine. Her neurological examination revealed impaired sacral sensations. There was no evidence of spinal dysraphism. Urological evaluation revealed a neurogenic bladder with chronic cystitis.

Neuroimaging

Magnetic resonance imaging (MRI) of the spine revealed a 5.1 cm × 4.3 cm × 2.9 cm sized intradural tumor from L5 to S2 levels. It was isointense on T1-weighted images, hyperintense on T2-weighted images, and demonstrated mild peripheral contrast enhancement [Figure 1]a-h. It had an extraspinal extension through the right S1-2 foramen. Computed tomography (CT) of the lumbosacral spine showed a widened right S1-2 neural foramen and scalloping of the posterior portions of the S1 and S2 vertebrae [Figure 2]a-f. Based on these findings, a radiological diagnosis of a long-standing benign nerve sheath tumor (schwannoma/neurofibroma) was considered.

At surgery, a defect in the right S1 lamina was noted overlying the bulged-out dura. There was no evidence of spinal dysraphism. Following partial L5, S1, and S2 laminectomies and durotomy, a soft, pearly white lesion was encountered [Figure 3]a-c. It had pushed the roots to the left side. The filum terminale appeared normal. The lesion and its capsule were excised totally. Histopathology was reported as epidermoid [Figure 4]a and b.

Postoperatively, she did not develop any new neurological deficit. A postoperative MRI with diffusion-weighted (DW) sequences done showed no obvious residue [Figure 5]a and b. She was discharged on a tapering dose of oral steroids to prevent aseptic meningitis. At 6 months of follow-up period, the patient was doing well; however, her urinary incontinence had remained the same.

Epidermoid cysts (ECs) are uncommon benign lesions with an incidence of less than 1% in the spine. [16],[17] They commonly present in the fourth decade with a slight male preponderance. [18] Described by Cruveilhier as tumeurs perlées (pearly white tumors) [18] due to their gross appearance, they consist of soft, whitish, keratin material without any element of skin appendage. [19] Congenital ECs are frequently found in association with spinal dysraphic conditions such as tethered cord, low lying conus, dermal sinus, or spina bifida, [20] while acquired ECs occur, following repeated lumbar punctures or trauma. [19],[20]

Among the SEs, the thoracic region is the commonest site of occurrence, followed by the sacral and cervical regions. [21],[22] In addition to the few reports of sacral SEs in indexed literature [Table 1], there are reports as well of presacral ECs occurring as a component of CS or Currarino triad (anorectal stenosis, defect in the sacral bone and a presacral mass). Additionally, there have been reports of the lesion occurring with an anterior sacral meningocele, [13],[14] a presacral meningeal cyst that occurs due to agenesis of a portion of the anterior sacrum.

Clinically, sacral SEs often remain asymptomatic due to the accommodative capacity of the sacral spinal canal. They generally exhibit extensions in a cephalad direction into the lumbar canal or laterally through the neural foramina. They may extend ventrally as well, breaching the anterior or posterior sacral wall. [23] Urinary dysfunction with or without back pain may be the presenting symptom, as in our case. Other cases may present with cutaneous manifestations of spinal dysraphism or meningitis. [24]

MRI is the imaging modality of choice for the diagnosis of a sacral SE. The tumor is classically a nonenhancing lesion of cerebrospinal fluid intensity that is isointense or hypointense on T1-weighted sequences and hyperintense on T2-weighted sequences. [20] Discrepancy in the intensity characteristics occur due to varying lipid and protein components. Abnormalities in vertebral bodies or posterior elements may be evident in long-standing lesions. DW imaging demonstrates restricted diffusion such as in ECs elsewhere, and may be of benefit while evaluating a cystic sacral lesion. [2]

Total excision remains the treatment of choice in symptomatic SEs compressing the thecal sac. [20] However, a densely adherent capsule may preclude total excision, [21] resulting in early relapses. Residual cystic contents predispose to the occurrence of aseptic meningitis in the postoperative period, a major complication that can result in the development of normal pressure hydrocephalus. [17],[22],[24]

Conclusions

SEs in the sacral region are rare. This is the third report of a sacral intradural SE occurring in a non-dysraphic spine. Epidermoid should be considered in the differential diagnosis of an intradural sacral tumour. When suspected, the radiological evaluation of such a lesion should include diffusion weighted imaging.

Financial support and sponsorship

The authors have not received any support, in the form of a grant, from any source for preparation of this article. Neither do the authors, nor does the institute have any personal or institutional financial interest in drugs, materials, or devices described in their submissions.

Hamby WB. Tumors in the spinal canal in childhood. II. Analysis of the literature of a subsequent decade (1933-1942); report of a case of meningitis due to an intramedullary epidermoid communicating with a dermal sinus. J Neuropathol Exp Neurol 1944;3:397-412.